The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
Diesel engine systems are popular due to their generally high efficiency relative to other kinds of internal combustion engines. This efficiency is due, in part, to the increased compression ratio of the Diesel combustion process and the higher energy density of Diesel fuel. However, the Diesel combustion process does produce particulates that are carried in the exhaust gas produced by the Diesel engine system.
A Diesel particulate filter is often used to remove these particulates from the exhaust gases. Typically, the Diesel particulate filter is coupled to the exhaust system downstream of the Diesel engine. The Diesel particulate filter receives the exhaust gas and filters particulates out of the exhaust gas. While useful for its intended purpose, the Diesel particulate filter can become full over time, and if not cleaned, the operating effectiveness of the Diesel particulate filter can be degraded.
Another solution known in the art is to use a regeneration process to remove particulates trapped in the Diesel particulate filter. These regeneration processes may take various forms, such as, for example, exhaust gas recirculation or using post-combustion fuel injected into the cylinder in order to raise the temperature of the exhaust gas stream. An exemplary regeneration process is found in commonly owned U.S. Pat. No. 7,104,048 B2, hereby incorporated by reference as if fully disclosed herein. These regeneration processes typically heat the exhaust gasses to a high temperature in order to burn the particulates from the Diesel particulate filter.
During conditions when the Diesel engine system is in an idle state, it is desirable to cool the exhaust gasses before they are expelled into the environment. Accordingly, an exhaust gas cooler may be coupled to the Diesel engine system downstream of the Diesel particulate filter to cool the exhaust gas. The exhaust gas cooler is operable to mix the hot exhaust gas with the cooler ambient air, thereby reducing the temperature of the exhaust gas. To do so, however, the amount of exhaust gas entering the exhaust cooler is typically restricted such that sufficient cooling can take place. This restriction of the exhaust gas can lead to back pressure, lowered horsepower, and other inefficiencies in the Diesel engine system when the Diesel engine system is running at a non-idle state and producing large amounts of exhaust gas. Accordingly, there is room in the art for an exhaust cooler that is operable to vary the amount of exhaust gas entering the exhaust cooler based on the operating state of the Diesel engine system.